An electric motor has six basic parts: an axle, at least one field magnet surrounding at least in part the rotor in its plane of rotation, commutator bars, a battery in the case of a direct current motor or an alternating current power supply in the case of an AC motor, brushes, and an armature.
The motor will turn due to the creation of magnetic forces at the ends of the armature that oppose those of the field magnet. The armature is an electromagnet made by wrapping wire around a metallic core. Each side of the armature is wrapped by an independent coil of wire, one connected to a first commutator bar, the other connected to the other commutator bar.
The armature and commutator bars are attached to the axle and spin around with the axle when power is supplied to motor from the power supply via the respective positive and negative electrical contact brushes, which are stationary with respect to the axle. The brushes by turn contact with the commutator bars which then polarize the coils on the opposite sides of the armature. Initially the positive end of the field magnet is aligned with the coil that has the positive polarity and the negative side of the field magnet is aligned with the coil that has the negative polarity. The repelling like forces cause the armature to rotate on the axle along with the commutator bars.
When the commutator bars rotate far enough, the brushes contact the respective commutator bars, which reverses the polarization on each coil so that the repelling force is renewed after the armature has turned 180 degrees, forcing a continuing rotation of the armature on the axle.
It is possible to use an electomagnet in place of a single or double field magnet for the motor, allowing an increase of current to the electromagnet and to the brushes, to provide control or increased magnetic field strength on demand when more rotational force is required from the motor.
There exist direct current motors utilizing permanent magnets to affect the operation of the rotor within the motor. A prime use of permanent magnets is to facilitate brushless DC motors. Permanent magnets can be placed perpendicular to the magnetic field of the main magnets of a rotor or stator to increase the flux density of the main magnets in a motor.